The present invention relates generally to golf balls and more particularly to an improved distance golf ball having a perforated inner shell positioned in the core in such a manner that it reduces the overall deformation of the ball when it is impacted by a golf club thereby increasing the travel of the ball.
Conventional golf balls can be divided into two general types: two-piece balls and three-piece balls (also known as wound balls).
Two-piece balls are made with a one-piece compressible, resilient core encased by a cover material. The core is usually made of a compression- or injection-molded cross-linked rubber such as a chemically cross-linked polybutadiene and has about the same size as a wound core, i.e., approximately 1.45 to 1.61 inches in diameter. The cover is generally injection molded or compression molded about the core and may be comprised of a urethane material, a synthetic balata rubber material, or a blend of ionomer resins, such as the various grades of ionomer resins produced by DuPont which are trademarked SURLYN, or the various types of ionomer resins produced by EXXON CHEMICAL which are trademarked IOTEK.
Three-piece balls, also known as wound balls, typically have either a solid rubber or liquid-filled bladder center core which may vary in diameter from xe2x85x9c of an inch to 1{fraction (1/16)} inches. Such center cores are then tightly wound with elastic thread to form a complete core which may have a diameter of approximately 1.45 to 1.61 inches. The complete wound core is then covered with a urethane, balata, ionomer, or similar material. The cover material is usually either compression molded or injection molded around the wound core to form a final ball that typically measures 1.68 inches in diameter. As a result of their more complex structure, wound balls generally require a longer time to manufacture and are more expensive to produce than one- or two-piece balls.
Multi-piece golf balls are also known and come in various forms. For example, a golf ball has been disclosed that includes at least five parts including a three-part solid core having a center section surrounded by two outer layers molded one about the other, each made of a elastomeric material to form the entire center core, and two cover layers made up of differing blends of ionomer type resins wherein the inner cover layer may be harder or softer than the outer dimpled cover layer. Purportedly, this ball travels a satisfactory distance and may have its coefficient of restitution, feel, and spin rate adjusted by changing the chemical composition of the various polymer blends that make up its multi-piece core and covers.
Golf balls are also disclosed that contain either one-piece solid cores or two-piece wound cores with two or more layers of cover material. The harder inner cover layers of these balls purportedly increase the coefficient of restitution of these balls and promote increased travel, and the softer dimpled outer covers purportedly increase the softer feel and the spin rates of these balls.
Other golf balls are also disclosed that contain solid spherical metal cores, metal cores of various shapes and diameters, and cores containing steel balls; the purpose usually being to increase the ball""s flight (also referred to as travel or distance) and to create more accurate flight. Such prior art golf balls, however, are impractical because they are too expensive to manufacture, and have undesirable characteristics such as heavy centers and lighter exteriors which increase the spin rates of these balls to undesirable levels, or because their design would not be sanctioned by the United Sates Golf Association for use in tournament play.
A ball incorporating a resilient, springy, perforated metal sphere near its outer circumference to maintain the shape and integrity of a cover made of unstable gutta-percha and prevent the gutta-percha from becoming misshapen when struck with a golf club is also known, and is described in U.S. Pat. No. 705,249. Gutta-percha, a tree sap in its natural gum form, was utilized as a golf ball cover material in the late 1800s and early 1900s. By reason of being mounted just beneath the surface of the gutta-percha cover whereby portions of the gutta-percha were forced into the perforations, the flexible, springy, perforated metal shell of this golf ball served to reinforce the unstable gutta-percha cover and help it from becoming misshapen when struck with a golf club, rendering the ball dead under a light blow. Col. 1, 11. 49-51.
It should be noted that all known golf balls may be made larger than (but not smaller than) the accepted 1.68 inch diameter size and still be approved for tournament play by the United States Golf Association.
There remains a need for a multi-piece, three piece, two-piece, or one-piece ball that has longer travel relative to its compression.
The present invention improves upon the prior art by providing a golf ball including: (1) an inner core comprised of a compressible or flexible material, such as cross-linked rubber or a liquid-filled bladder, (2) a perforated barrier shell positioned around the inner center core, (3) an outer core comprised of either (a) a compressible elastomeric material, such as cross-linked rubber or plastic of the type that forms the inner core, or a synthetic polymer gel-type material (b) layers of such material(s), or (c) layers of tightly wound elastic thread, and (4) a dimpled outer cover, which may be comprised of one or more layers, and made of thermoplastic elastomers, urethane elastomers, either natural or synthetic balata rubber, various grades, types, and blends of ionomer resins such as SURLYN manufactured by DuPont or IOTEK manufactured by Exxon Chemical, or combinations thereof.
Preferably having a common center with the inner core of the golf ball, the perforated barrier shell is preferably spherical and may have a diameter ranging from approximately 0.35 inches to approximately 1.26 inches depending upon the desired coefficient of restitution of the golf ball and its desired degree of hardness (feel) relative to the composition and type of the golf ball""s outer core.
The theory of why it is believed a ball including the perforated barrier shell of the invention has superior characteristics shall now be explained. It will be understood, however, that the invention is not limited by any particular theory and that the scope of protection afforded the invention is set forth in the claims. When the golf ball is struck by a golf club, the ball is compressed or forced into an out-of-round shape with its area of contact actually flattening against the face of the club. The perforated barrier shell is designed to allow for compression and to promote the increased rebound of the ball, which leads to longer flight. As is generally represented in FIG. 5a, the perforated barrier shell reduces the overall amount the ball is pushed into an out-of-round shape by arresting and confining a portion of the force created by the golf club to the area of the ball located between the club face and the surface of the barrier shell closest to the club""s point of impact, thereby preventing a portion of this force from passing through the barrier shell and contributing to the overall deformation of the ball""s entire mass. When allowed to flow unrestricted throughout the entire ball, much of this force is dissipated in the non-productive generation of heat energy and absorbed in the non-productive distortion of areas of the ball located away from the point of impact. The perforated barrier shell thus reduces the amount of energy normally devoted to the non-productive deformation of the golf ball""s entire mass and serves to reflect this energy back against the face of the golf club thereby utilizing the redirected energy to enhance the ball""s coefficient of restitution and increase its rebound speed and length of travel. Therefore, use of the present invention permits golfers to obtain longer distance with the same swing speed, or the same distance with lower compression balls utilizing the present invention as with known balls of higher compression ratings.
In addition to decreasing the overall deformation of the golf ball when it is struck with a golf club, in many embodiments of the invention, the ball""s outer and inner core materials come into direct physical contact with each other as they are forced into and through perforations in the barrier shell when the ball is compressed with a golf club. A portion of the energy generated by the golf club impacting the ball is thus transmitted through the openings or perforations in the barrier shell directly from the club""s point of impact through the ball""s cover and outer core material, into the inner core material, and through it to the opposing portion of the outer core material(s). Thus, as a result of the perforations in the barrier shell, the inner and outer core materials provide a continuous physical medium for the partial transfer of the energy and/or force generated by the club""s impact through the center of the ball instead of forcing this energy to completely circumvent the inner core material.
Further, if the barrier shell did not include perforations to permit energy to pass through it, some of the energy/force generated by the ball""s compression would not be permitted to pass through the center core material. In that case, more of this energy/force could then be made to travel in one direction around the perimeter of the barrier shell and the energy/force could thus be skewed off center. Since this unbalanced transfer of energy could cause the ball to be compressed to a greater degree in one portion of the ball""s impact area and thereby exert uneven rebound pressure back against the face of the club, the ball could be thrust off line at an undesirable angle away from its intended line of flight as it rebounds off the club face. This condition could also cause the ball to assume a severe lateral spin bias resulting in unwanted hooks or slices which would cause the ball to curve left or right of the desired target line. It should be noted that both of these situations would be exacerbated by off-center hits, i.e., impacts by a club not delivered perfectly square, or wherein the club face is not perpendicular to the desired direction of travel when it strikes the ball. Common among golfers of all skill levels, such off-center hits would thus cause an even more unbalanced transfer of energy/force back against the club face if none or little of the energy/force generated by the ball""s compression were able to pass through the center of the ball.